(1) Field of the Invention
This invention relates to a method for correcting certain causes which lead to deterioration of the picture quality and which occur in a television camera system, especially in a camera lens, an optical system such as color-separating optical system, pickup devices and the like, and an electric circuit system.
(2) Description of the Prior Art
In the case of a color television camera making use of a plurality of pickup devices, the following various adjustments or corrections have conventionally been effected under certain specific conditions, namely, using a prescribed image pickup lens, a specific color-separating optical system and particular pickup devices with prescribed object distance and focal length under specific illumination:
(1) registration of the positions of images among various channels (hereinafter called "registration adjustment");
(2) registration of the focal points among the pickup devices in various channels (hereinafter called "focus tracking adjustment");
(3) adjustment of irregularity of picture signal levels among various channels when shot under the same brightness level (hereinafter called "shading adjustment");
(4) adjustment of the color reproducibility when a color chart is shot (hereinafter called "adjustment of color reproducibility"); and
(5) adjustment of distortion of an image in each channel (hereinafter called "distortion adjustment").
However, the brightness, object distance and focal length will change in various ways depending on scenes to be shot when a television camera system is actually operated. Therefore, it is necessary to set the iris value and zoom ratio of each image pickup lens and the object distance at various values in accordance with the scenes to be shot. In addition, the lens may be replaced depending on the scene to be shot. When the lens is replaced or a image pickup condition such as the iris value, zoom ratio or object distance changes, image pickup characteristics such as the aberration characteristic, shading characteristic and distortion characteristic of the lens are also changed correspondingly. The levels of adjustments (1)-(5) obtained by using a prescribed pickup lens with specific object and focal length under a prescribed brightness level upon adjustment of the televison camera system may become unsuitable during an operation of the television camera system, thereby developing a problem that the thus-adjusted pickup characteristics may be offset from desirable pickup characteristics.
Besides, elements or devices to be used, such as the above-described lenses, pickup devices and the like have certain characteristics which vary depending on the time or temperature. Accordingly, there has been another problem that the chracteristics may become offset from their corresponding optimum values, which have in advance been adjusted upon adjustment of the television camera system, during the passage of the time or in accordance with temperature variations in the system.